NASCAR hit the No. 11 Joe Gibbs Racing team with a points penalty of unprecedented magnitude for infractions discovered during Sunday’s post-race inspection at Indianapolis Motor Speedway, the sanctioning body announced late Tuesday afternoon.

NASCAR inspectors found violations with the rear firewall block-off plates of the No. 11 Toyota driven to a third-place finish by Denny Hamlin. NASCAR rules mandate that the firewalls be sealed to prevent airflow from the inside to the outside of the car.

Venting or failing to seal the block-off plates can provide an aerodynamic advantage by adding downforce to the car, especially useful at a flat track such as IMS, where maintaining momentum through the corners is of paramount importance.

NASCAR docked Hamlin 75 driver championship points and team owner Joe Gibbs 75 owner points. Crew chief Darian Grubb was fined $125,000 and suspended for six weeks, meaning he will be lost to the team until the Chase for the NASCAR Sprint Cup’s opening weekend at Chicagoland Speedway in September.

Car chief Wesley Sherrill also drew a six-week suspension. Both Grubb and Sherrill were placed on probation for the next six months.

The points penalty is the largest since NASCAR instituted its new one-point-per-position scoring system in 2011. And since 75 points are the functional equivalent of 312 under the previously-used Latford scoring system, the points penalty is the largest ever imposed.

Joe Gibbs Racing issued a statement after the penalties were announced indicating the organization’s intent to appeal the penalties. Grubb and Sherrill, however, will begin serving their suspensions this week and will miss this weekend’s NASCAR activities at Pocono Raceway in Long Pond, Pa.

The infractions rose to the level of P5 under the new deterrence system introduced by NASCAR before the 2014 season. P6 is the designation for the most egregious violations.

NASCAR indicated on Sunday at the Brickyard that there were “possible issues” with the rear firewall block-off plates of the No. 11. The sanctioning body confiscated the parts in question, took them to the NASCAR Research and Development Center in Concord, N.C., for further inspection and evaluation and announced the findings and penalties on Tuesday.